What is a thesis?

Defining the thesis

Thesis is derived from Greek, in which the word has the sense of a proposition. The essential meaning of thesis (which will here be treated as roughly interchangeable with hypothesis) has thus remained stable from its ancient Greek origins into today’s English: a thesis is a proposition, affirmation, or assertion that can occur in literature, rhetoric, science, mathematics, or even everyday talk.

Before attempting a more formal definition of thesis, it will help to consider the following examples of theses:

  • Some examples of theses:
  • Literature: To be or not to be, that is the question.
  • Rhetoric: The death penalty is barbaric.
  • Science: All organisms evolved from simpler organisms due to natural selection and mutation.
  • Ordinary Conversation: The weather will be pleasant tomorrow.

What do these theses have in common?

On further introspection, each thesis makes some kind of claim about what is true; each thesis has what philosophers call truth value. Now, it may be that the truth value of a thesis is false; for example, a thesis that the weather is warm when the temperature is actually below freezing is false. The point, however, is that the thesis will in principle be capable of being true or false. This is an important point, because it helps us to understand what theses are not. Orchestral music is not a thesis; sculptures are not theses; the babbling of a baby is not a thesis; in short, any statement that is not a proposition with truth value is not a thesis.

Thesis versus tautology

On the other hand, complicating our attempt to provide a definition of thesis, not all propositions with truth values are theses! Consider the following geometrical statement: “In any right triangle, the square of the longest side equals the square of the second side plus the square of the third side.” This statement is always, and by definition, true. It is in fact a tautology, which in logic is the equivalent of saying “A = A.” Harking back to Greek etymology, a thesis is an assertion to be examined for its truth value; a thesis is an invitation to speculate on the soundness and/or validity of a statement. Is it true, as Hamlet invites us to believe, that death is better than life? Is it true that the death penalty is barbaric?

Is it true that the weather will be pleasant tomorrow? It depends on the arguments put forward, and on the preconceptions and tastes of the listener. What do you consider pleasant weather? Why do you choose to live rather than die?

The thesis, although put in the form of a statement that can be true, never is true in the same way that a tautology is true; it is an invitation to think about the truth of something in what can be highly subjective ways, and the final conclusion is not universally valid in the same way that a mathematic thesis is universally valid. We are free to reject a thesis, be it howsoever expertly and compellingly argued, but we are not free to reject the law of gravity or the geometrical properties of triangles.

What is a good thesis?

This leads us closer to a definition of thesis. A thesis is a propositional statement or set of such statements—expandable to any length, from a single sentence to a book—that can be true or false, but which we are nonetheless free to reject based on the evidence and our reaction to it. This is a broad definition, and one that has the advantage of capturing the similarities between otherwise disparate kinds of theses, but not one that is helpful in deciding what is a good thesis, especially a thesis advanced in the formal atmosphere of an essay. Here are some possibilities:

  • The thesis can be interesting. If advancing a thesis is part of the ancient art of the rhetoric, the trick is to keep the audience engaged. Arguing that murder is never justified is uninteresting; arguing that murder can be justified is more interesting.
  • The thesis can marshal new evidence for an old assertion, or derive rhetorical support from an unlikely source. Thus, recent theses that the suspicion of women that appears in some of Shakespeare’s plays could be conditioned by Shakespeare’s venereal disease are compelling.
  • Even if largely unoriginal, the thesis can be distinguished by an extreme attention to detail: for example, by appealing to a wide range of reference materials.
  • We have thus progressed from defining a thesis to discussing how some theses might be better than others because of the use of compelling propositions, evidence, and detail. These theses about theses will be tested out and expanded upon in the sections to come.


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